Hydraulically operated bit drive



Aug. 5, 1958 E. w. SMITH 1 HYDRAULICALLY OPERATED BITMDRIVE Filed Feb. 20. 1953 www u iv l I v.

United States Patent HY DRAULICALLY OPERATED BIT DRIVE Edward W. Smith, Melrose Highlands, Mass. Application February 20, 1953, Serial No. 338,056

9 Claims. (Cl. 255-44) The present invention relates to earth boring tools and method of driving them and more particularly to the type where impact of the cutting tool against the formation to be bored is used to give the desired cutting actron.

There has been a considerable amount of interest in methods for utilizing the advantages of impact cutting either alone or in combination with rotation on equipment utilizing drilling fluid and many attempts have been made to accomplish it as for instance by spring actuated hammers or ratchet methods of raising and dropping weights to provide impact on the tool, but for the most part such arrangements have been either too complicated and expensive, or provided insuflicient energy to do the work required.

In the arrangement presently to be described, means are provided for generating relatively high frequency energy in a simple and effective manner directly above the tool where it is to be used and at the rate of 10 horsepower or more as will appear.

One of the purposes of the present invention is to deliver the primary power from which the high frequency energy is converted, via the moving mud column itself.

Another purpose of the invention is to provide a source of high frequency energy at the cutting element and at a rate providing substantial amounts of power.

Another purpose of the invention is to provide an arrangement whereby rotational energy may be supplied to the tool independently of the impact arrangement so that it may be supplied simultaneously with the impact energy or not as may be desired.

Still another purpose of the invention is to provide an arrangement whereby drilling mud can be delivered to the cutting tool as is usual in rotary drilling.

Another purpose of the invention is to provide the means necessary for doing this in a form which can readily be connected to the drill stern between the drill stem and the tool without any other alterations.

In the specification below, some terms are used which may have different meanings in other arts. Highly elastic, as herein used refers to the modulus of elasticity such as Youngs modulus wherein steel is more elastic than rubber and is defined in terms of pounds per square inch or force applied per unit area times the deflection per unit length.

The word mass refers to a concentrated mass either a solid, or a solid with bore holes where the utility requires it, or a thick cylinder of heavy metal where the utility requires it.

The words highly elastic member or tube refers to a rod or tube efficiently used to store up potential energy by direct compression or tension as the result of applied forces which energy is released as kinetic energy when the force is removed.

The term cylinder herein includes any substantially regular polygon or oval shaped device when serving substantially the same purposes as the corresponding terms used in the specification.

Further advantages and improvements will be better understood when considered in connection with the drawings showing an embodiment of the invention in which:

Figure 1 shows a longitudinally broken section through the device,

Figure 2 shows a section on 2-2 of Figure 1,

Figure 3 shows a section on 33 of Figure 1, and

Figure 4 shows a conventional structure employing the present invention.

Before entering into the description of the drawings, it may be well to note that the device shown may be adapted for a rotary drill or an impact drill alone. The cutting or impact tool in either case will be attached at the right end of the device shown in Figure 1, and Figure 4 at 20 and the drive at the left end of Figure 1 and Figure 4 by the motor 21 and gear 22 secured to the shaft 13. So-called drilling mud will enter through the hollow shaft 13 into the chamber formed by the cap 12 while a rotating driving element will drive the hollow shaft 13. It will be appreciated that compressed gases or air could be substituted for the drilling mud to provide the desired pressure.

The means whereby the purposes of the invention are accomplished can best be understood from a reference to Figure 1, where 1 represents the outer casing on the unit now to be described in detail.

Internally of the outer casing 1, a mass element 2 is disposed concentric with it and free to move axially within casing 1 when permitted by the elongation or contraction of tube 3 to which it is solidly secured. It will be noted that the end of element 2 at which it is secured to tube 3, has been reduced in diameter to accommodate a cylinder 4 which fits snugly over it and serves to secure in position the replaceable element 5 which together with element 6, similarly secured in casing 1 by sleeve 7, forms the faces of a sleeve valve which opens and closes an annular access to an annular opening between the interior of casing 1 and element 2, connecting it periodically to the space 8 between the casing 1 and tube 3.

It will also be noted that element 2 at its outer end has projecting strips 9 which bear on the inner surface of liner tube 7 and act as guides to ensure accurate alignment of the axis of element 2 with axis of casing 1.

It will be observed that casing 1 and its supporting structure 10 form a backing mass which I prefer to make large i. e. eight or ten times the mass of element 2 which carries the cutting tool. It will also be noted that the supporting structure 10 has openings 11 passing through it which connect space 8 with the cap 12 and the interior of drill stem 13.

It will be clear from the above that in operation, some of the drilling mud passing downward through drill stem 13 will go directly through the central opening 15 in supporting structure 10, through pipe 3 and the central opening in element 2, and thence outward to the cutting edges of the tool in the usual manner. The rest of the downflowing mud from drill stem 13 passes through openings 11 into space 8 where it exerts a pressure against element 2 since the annular sleeve valve formed by elements 5 and 6 is normally closed. However as the pressure exerted by the mud increases, tube 3 is stretched allowing the just mentioned sleeve valve to open bringing about a sudden drop in pressure against element 2 and discharging a certain amount of the mud downward through the annular space between element 2 and the casing 1 and outward into the hole from which it returns to the surface in the usual manner along with the mud which passes through the bit. When this happens, the force exerted by the stretched tube 3 no longer is balanced by the mud pressure in space 8 and element 2 is retracted closing the sleeve valve, and the process is repeated. By proper adjustment of the size of the hole in bushing 14, the amount of mud necessary for the operation of the unit may be diverted from the main stream passing through to the tool.

From the above description it will be understood that the mass of element 2 plus that of the tool to which it is secured, in combination with the longitudinal stiffness of tube 3 forms a resonant system whose frequency is a'func tion of the magnitudes of the mass involved and the stifiness of tube 3. While itmight be assumed by those not thoroughly conversant with such systems, that the stresses set up in tube 3 by the axial vibration of element 2 would be likely to fracture it, actually this is not the case provided that the design of the system takes this problem into account. Thus, for example, if the weight of element 2 plus the tool to which it is connected weigh, let us say 600 pounds, then the tube 3 must be subjected to a stress of 28,100 pounds for resonance at 3600 vibrations per minute with a stroke of inch. In other words, tube 3 is elongated and compressed inch 3600 times per minute. Then if tube 3 is made to have an axial length of substantially 21 feet, the maximum fiber stress in the tube will not exceed approximately 15,000 lbs./ sq. in. if the cross sectional area of tube 3 is made 1.843 sq. in. Such a cross sectional area would be provided by this length of 2% inches 0. D. seamless drill pipe having a wall thickness of .28 inch. I have found no difiiculties in the more or less continuous cyclical stressing of high grade steels if such a fiber stress as this is not exceeded.

Such a unit as has been described above can readily deliver impacts of the order of 100 foot pounds at the rate of 3600 per minute which is roughly the energy equivalent of a 4000 pound cable tool string dropped through a distance of 30 inches at the rate of 30 strokes per minute.

For the horsepower indicated above, i. e. approximately H. P. the frequency of 3600 vibrations per minute is especially suitable as will be clear from the fact that at such a frequency the amplitude of motion of element 2 either side of the position at rest can well be /a inch where element 2 is of the size mentioned above. This in turn dictates the length of the active portion of tube 3 if a fiber stress of 15,000 lbs/sq. in. or thereabouts, is not to be exceeded.

The overall length of the tube 3, together with element 2 and backing mass 10, then becomes less than 60 feet which is an overall length which can be readily handled on the average drill rig.

This frequency has another advantage in that since the unit is an hydraulically operated device, account must be taken of the velocity of compressional waves in the liquid used. For example, the velocity of transmission of such waves in an aqueous media is in the neighborhood of 4800 feet per second. With element 2 reciprocating at 3600 vibrations per minute the liquidin space 8 will be subjected to pulsating pressure due to the reciprocation of element 2. Therefore the wave length of the pulsation at this frequency Will be approximately 80 feet or have a quarter wave length of approximately 20 feet which, it will be recalled, is substantially the active length of tube 3 so that they tend to aid rather than otherwise the vibration of element 2.

Care should therefore be taken to see that substantially such relationships as have just been described, exist between the length of space 8 and the operating frequency so that standing wave pulsations in the liquid mud in space 8 tend to assist rather than interfere with the reciprocation of element 2.

It will be clear from the above description that in the present invention reciprocation of element 2 in no way interferes with the rotation of the bit in the usual way since the torque necessary to rotate the tool is transmitted by tube 3 which may Well be as previously mentioned, a piece of drill pipe of the proper dimensions and which has already been designed for the transmission of substantial torque.

Mention was made earlier of the fact that I prefer to make the mass of the backing structure 10, large, i. e. 8 to 10 times that of the mass element 2. There is a definite reason for this because by so doing, the possible motion of the backing mass as compared to that of element 2 is reduced in the same proportion thereby tending to reduce the transmission of any of the impact energy back up along the drill stem to the surface where it might be objectionable.

Having now described my invention, I claim:

1. In combination with an earth boring tool, a cylindrical member of substantially rigid material having a longitudinal central bore for furnishing fiuid to the boring tool and means including at least one smaller bore parallel thereto diverting fluid from the boring tool, a highly elastic tube fitting to said member at the end and providing a passage as a continuation of said central bore, a second cylindrical substantially rigid member having a central bore firmly secured to the other end of said highly elastic vtube, a further cylinder extending from the outer surface of said first cylindrical member coaxial with, but of larger inner diameter than said elastic tube and juxtapositioncd to said second cylindrical member forming a chamber between the inner wall of Said further cylinder and said elastic tube with the ends of the first and second cylinders forming the end walls thereof, and the elastic tube and further cylinder forming the side walls thereof, and a valve means operable by fluid pressure supported in part on said second cylindrical member, and in part on said further cylinder at the end of the side walls of the chambers whereby when fluid is forced into the chamber periodic pulsations of the cylindrical members will take place.

2. In combination with an earth boring tool, a highly elastic resonant oscillatory system comprising a relatively stationary large mass element, a substantially relatively movable smaller mass element, said mass elements having a ratio of substantially 10:1, means having a high modulus of elasticity rigidly joined at one end to the large mass element and at the other end to said smaller mass element, a fluid valve having a part carried by said relatively movable mass element, a cooperating part carried by said relatively stationary mass element, means for exerting pressure between said mass elements causing periodic oscillatory movement thereof through the operation of said valve.

3. In combination with an earth boring tool a highly elastic oscillatory system comprising means providing mass members, a highly elastic member rigidly joined at each end, one to one mass member and the other to a second mass member, said mass members having a ratio of substantially 1021, a fluid chamber formed by said members, a valve provided at one end of said chamber having a part carried by each of said mass members, means providing fluid pressure to said chamber for stretching said elastic member and oscillating said mass members by periodically opening said valves against the strain of said elastic member.

4. In combination with an earth boring tool, a cylindrical member of substantially rigid material having a longitudinal central bore for furnishing fluid to the boring tool and means including at least one smaller bore parallel thereto, a highly elastic tube fitting to said member at one end and providing a passage as a continuation of said central bore, a second cylindrical substantially rigid member having a central bore firmly secured to the other end of the said highly elastic tube, a further cylinder extending from the outer surface of said first cylindrical member coaxial with, but of larger inner diameter than said elastic tube and juxtapositioned to said second cylindrical member forming a chamber between the inner wall of said further cylinder and said elastic tube with the ends of the first and second cylinders forming the end walls thereof, and the elastic tube and further cylinders forming the side walls thereof, and a valve formed at the lower end of the chamber having one part in the outer wall of the second cylindrical member and the other part in the inner wall of the further cylindrical member opposed to each other whereby when the parts oscillate with respect to each other, the valve will open and close.

5. In combination with an earth boring tool a cylindrical member of substantially rigid material having a longitudinal central bore for furnishing fluid to the boring tool and means including at least one smaller bore parallel thereto, a highly elastic tube fitting to said member at one end providing a passage as a continuation of.

said central bore, a second cylindrical substantially rigid member having a central bore firmly secured to the other end of said highly elastic tube, a further cylinder extending downward from the outer surface of said first cylindrical member coaxial with, but of larger inner diameter than said elastic tube and juxtapositioned to said second cylindrical member forming a chamber having an opening for receiving the diverted fluid between the inner wall of said further cylinder and said elastic tube with the ends of the first and second cylinders forming the end walls thereof, and the elastic tube and further cylinder forming the side walls thereof, and a valve formed at the lower end of the chamber having one part in the outer wall of the second cylindrical member and the other part in the inner wall of the further cylindrical member, said parts being positioned to move in parallel planes in opposite directions and having abutting surfaces inclined to said planes in radial alignment with the coaxial axis whereby when motion is in one direction, said valve will close and in the opposite direction, said valve will open.

6. In combination with an earth boring tool a cylindrical member of substantially rigid material having a longitudinal central bore and at least one smaller bore par allel thereto, a highly elastic tube fitting to said member at one end and providing a passage as a continuation of said central bore, a second cylindrical substantially rigid member having a central bore firmly secured to the other end of said highly elastic tube, a further cylinder extending downward from the outer surface of said first cylindrical member coaxial with, but of larger inner diameter than said elastic tube and juxtapositioned to said second cylindrical member forming a chamber between the inner wall of said further cylinder and said elastic tube with the ends of the first and second cylinders forming the end walls thereof, and the elastic tube and further cylinder forming the side walls thereof, and an annular valve means having one annular element carried by said second cylindrical member and the other annular element by said further cylinder in juxtaposition thereto, said valve having surfaces adapted to be closed in one position of motion of the members and open in another position.

7. A system as in claim 6, in which said annular valve means are removably fixed and include a shoulder on which each part rests with a sleeve securing the parts of the valve means in place.

8. In combination with an earth boring tool, a highly elastic oscillatory system comprising means providing mass members, a highly elastic member rigidly joined at each end, one to one mass member and the other to a second mass member, a fluid chamber formed by said members, a valve provided at one end of said chamber having a part carried by each of said mass members, means providing fluid pressure to said chamber for stretching said elastic member and oscillating said members by periodically opening said valves against the strain of said elastic member, said chamber being made resonant with said system whereby substantially maximum amplitude may be built up as one of said mass members.

9. In combination with an earth boring tool, a highly elastic oscillatory system comprising means providing mass members, a highly elastic member rigidly joined at each end, one to one mass member and the other to a second mass member, a fluid chamber formed by said members, a valve provided at one end of said chamber having a part carried by each of said mass members, means providing fluid pressure to said chamber for stretching said elastic member and oscillating said members by periodically opening said valves against the strain of said elastic member, said chamber formed to resonate at onefourth wave length of the resonant frequency of said systern.

References Cited in the file of this patent UNITED STATES PATENTS 

